This invention relates generally to steering columns and more particularly to an energy absorbing device for a collapsible steering column.
To protect a driver from severe injury in a frontal collision, many vehicles today are equipped with collapsible steering columns having energy absorbing devices to absorb some of the impact energy exerted on the driver""s body during the collision. Typically such devices are designed to protect drivers of average size and weight in a collision of average severity, without taking into account the fact that drivers are not all of average size and weight and that collisions vary considerably in severity depending upon vehicle speed at the time of impact. U.S. Pat. No. 5,788,278 discloses an M-strap energy absorbing system for a collapsible column having fixed anvils about which the strap deforms to absorb energy. The energy absorption characteristics are non-adjustable during a crash event.
In accordance with the present invention, provision is made for a adjusting the amount of resistance to the collapse of the steering column depending on a number of conditions including but not limited to the weight of the driver, position of the driver""s seat, and speed of the vehicle at impact. The device includes an energy absorber for imposing a resistance to collapse of the steering column when it collapses in a vehicle collision, and a load adjuster for adjusting the resistance to collapse imposed by the energy absorber. A controller is provided to produce a signal of a magnitude indicative of an amount of resistance needed to be imposed on the steering column to better protect from injury a driver seated behind the steering column at the time of the collision. The signal produced will be dependent upon the various parameters measured at the time of the collision. An actuator receives the signal and actuates the load adjuster to adjust the amount of resistance imposed in accordance with the magnitude of the signal.
More specifically, the energy absorbing device may comprise an elongated plastically deformable metal strap and the load adjuster may be in the form of an anvil. Preferably the strap is generally M-shaped having parallel legs and a generally V-shaped portion connecting corresponding ends of the legs. The anvil engages a concave side of the V-shaped portion and may be moved in opposite directions by the actuator to vary the amount of resistance to steering column collapse imposed by the strap.
Preferably the actuator is in the form of a hydraulic cylinder controlled by an electronic solenoid valve. Valves of this description have a very rapid response and can make adjustments in the position of the anvil in only a few milliseconds after impact, while the steering column is still collapsing.
Among the conditions that may be sensed and therefore employed to influence the position of the anvil, are the weight of the driver, the position of the driver""s seat, and vehicle speed at the time of impact.
One object of this invention is to provide an energy absorbing device having the foregoing features and capabilities.